This research program focuses on natural killing (NK) cell biology and the roles of these cells in defense against tumor and immunoregulation. Studies are pursued in four major areas: 1. Regulation of NK cell activity by various immunomodulators. We will assess the effects of synthetic interferon (IFN) gamma administration in cancer patients on NK activity. In vitro studies are planned to investigate the role of the lipoxygenase metabolites of the arachidonic acid pathway on endogenous NK activity and on the possible involvement of this pathway in activation by IFNs and poly I:C. Indeed, we have demonstrated that lipoxygenase inhibitors suppressed endogenous NK cell activity, whereas interferon or poly I:C activated NK cells were partially resistant to suppression by the inhibitors. These results suggest that products of lipoxygenation are required for maintenance of human NK activity. We will initiate studies with the tumor-associated P15E antigen, which in purified form suppresses mononuclear phagocyte function and might similarly affect tumor-associated NK cells. Preliminary data suggest that pISE does indeed inhibit NK cell activity. Our emphasis will be to study the effects of newly synthetized peptides with pISE sequences on NK and other cell-mediated responses. 2. Locomotion of NK cells. We found that purified NK cells have a polarized shape and are quite mobile. We will investigate whether NK cells are capable of chemotaxis in response to stimuli such as C5a and lymphokines. 3. Proliferative capacity of NK cells. We have developed an approach that will enable us to determine precisely whether NK-like cell lines are indeed the progeny of fresh NK cells as found in human peripheral blood. Low density cells obtained from Percoll gradients and further selected by monoclonal antibodies (MAbs) will be tested in short-\and long-term proliferative assays. 4. Heterogeneity of NK cell function. We have developed two novel methods for isolating NK cells independent of density or conventionally detected surface markers. These techniques in conjunction with panning by MAbs will be employed to detect minor and perhaps previously unrecognized populations of NK cells. Subsets of NK cells will be assessed for other functions including Ig synthesis, granulopoiesis, and gamma-IFN production. (LB)